Sending unit for electric speedometers



4 Sheets-Sheet 1 A. W. LE FEVRE SENDING UNIT FOR ELECTRIC SPIJEDOMETERS Filed OCT.. 2, 1936 July 8, 1941.

July 8, 1941. A w. LE FEVRE 2,248,711

SENDING UNIT FR ELECTRIC SPEEDOMETERS Filed Oct. 2, 1936 4 Sheets-Sheet 2 x d 130 if;

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SENDING'UNIT FOR ELECTRIC SPEEDOMETERS Filed Oct. 2, 19556 4 Sheets-Sheet 4 valen Wl/vne Patented July 8, 1941 Y SENDING UNIT FOR ELECTRIC SPEEDOMETERS Arden W. Le Fevrc, Chicago, Ill., asslgnor to Stewart-Warner Corporation, Chicago, lll.,

corporation of Virginia A y Application October 2, 1936, Serial No. 103,748

(c1. coi-4s) 14 Claims.'

My invention pertains to sending units for electric speedometers, particularly adapted for automobiles in which the engine is located at the rear of the vehicle, and is an improvement on the electric speedometer disclosed in application, Serial No. 40,600, led September 14', i935.

An object of my invention is to provide an improved sending means for electric speedometers.

Another object is to provide a sending means for electric speedometers which more accurately translates the true speed of the vehicle at all times.

Another object of my invention is to provide a sending means for electric speedometers which is simple and which will be free from operating difficulties.

Another object is to provide a sending means' for electric speedometers which is economical to manufacture.

Another object is to provide a sending means for electric speedometers in which the currentvarying means is less aiected by vehicle vibration.

Other objects and advantages will become apparent as the description proceeds.

In the drawings,

Figure 1 is a sectional view of a sending unit for electric speedometers embodying my invention. and shows this sending unit connected in Y an electrical circuit including speed and mileage-indicating means, the circuit and indicating means being diagrammatically shown.

Figure 2 is a transverse sectional view of the sending unit and is taken on the line 2-2 of Figure l; f

Figure 3 is another transverse sectional view of the sending unit and is taken on the line 3-3 of Figure 1;

Figure 4 is a partial sectional view showing a detail and is taken' on the line 4--4 of Figure 2;

Figure 5 is a longitudinal section of an improved form of my invention;-

Figure 6 is a side elevation on a reduced scale of the form of my invention shown in Figure 5;

Figure 7 is a transverse section taken on the line 'i-l of Figure 6;

Figure 8 is an end view looking in the direction of the arrow 8 of Figure 6;

Figure 9 is a transverse section taken on the line 9--9 of'Figure 6; and

Figure 10 is a view showing the switch mechanism and is a section taken on the line IU--ill of Figure 9.

In Figures 1 to 4 of the drawings I have shown my improved sending unit for electric speed,-

ometers as comprising a casting i0 of iron or other suitable magnetic material. This casting I8 is attached as by means of threads I2 to the part i4 of a transmission housing or .other suitable stationary part of an automobile or other vehicle.

The casting I8 includes bearing sleeves I6 and I8 carrying a magnet shaft 28 which forms a separable connection 22 with a driving shaft 24 mounted in the part I4. The shaft 24 may be l connected to or a part of the vehicle transmission or may be any other rotating part of the vehicle which rotates in a constant, predetermined speed relationship to one or more of the vehicle wheels.

'I'he magnet shaft 28 drives a cup-shaped magnet support 28 to which is attached a permanent magnet 28 bent into the form of an annulus but having its ends separated by a suitable gap which may either be left open or which may be filled with non-magnetic material, as desired. Across the ends of the magnet is a bypass regulator which is clamped between the bottom of the cup and a shoulder 32 in such manner that the bypass 30 may be manually swung about its axis relative to the magnet 28. It is to be understood that the magnet 28 may be further provided with any usual temperature compensator.

The adjacent cylindrical wall 34 of the casting I0 cooperates with the magnet 28 in setting up an intense magnetic held therebetween. In this field is located aspeed cup 88 of aluminum or other suitable material. This speed cup 38 is mounted on a shaft 88 joumalled in bearings 48 and 42. l

The bearing 40 comprises a jewel 44 mounted in a socket formed in the thin central portion of an insulating block 48 formed of a phenol condensation product or other suitable material.

The jewel '44 is held in place by a thin plate 48 attached to the central portion of the block 48 by hollow rivets 58. It is to be noted that the design and arrangement of the bearing 48 are such that this bearing and its support insulate the shaft 88 from the castingl l0.

The lower bearing 42 comprises a Jewel 52 which holds the shaft 38 against lateral movement, and a second jewel 54 which resists the longitudinal thrust of the shaft 88.

' f The jewels 52 and 54 insulate the lower end of the shaft 38 from the combined bearing support and oil shield 58. This oil shield and bearing support is made of brass or other non-magnetic material and is secured in place by the set screw 88, The jewels 52 and 54 are clamped in a socket formed in the support 58 by an annular plate 88 attached to the support 88 by rivets 82. From the foregoing description of the bearings 48 and 4-2, it will be seen that these bearings completely insulate the speed cup shaft 38 from the casting I8.

The speed cup 38 is attached to its supporting shaft 38 in such manner that the tendency of the speed cup 38 to rotate with the magnet 28 is transmitted to the shaft 38. This shaft also carries for rotation therewith contact finger 84 having a short flexible upper end 88 and a rigid lower end 88 firmly attached to the hub 18 for rotation with the shaft 38. This finger 84 is made of current-conducting material and forms an electrical connection between the shaft 38 and a point on the resistance 12 over which the contact finger 84 slides. The resistance 12 is arranged in the form of an incomplete circle and comprises a strip 14 of suitable insulating material about which is wound a nichrome or other high-resistance wire 16. The resistance 12 is located in an annular slot defining structure of C- shaped cross-section comprising the insulating blocks 48 and 18 which are preferably made of the same material. The blocks 48 and 18 are held in clamped relation about the resistance 12 by bolts 88 and 82 and nuts 84 and 88, respectively.

'I'he bolt 88 forms one electrical terminal of the sending unit and is in electrical communication with the shaft 38 and contact linger 84 through resilient plate 88 which engages one end of the shaft 38 and which has the further function of pressing this shaft lightly against the bearing jewel 54 so that longitudinal movement of the shaft is prevented. The plate 88 is clamped lbetween nuts 84 and 98. The extension of the outer end of the plate 88 into the vertical groove 82 formed in the insulating block 48 prevents pivotal movement of the plate 88 about the bolt 88.

The rotational movement of the speed cup 38 and its shaft 38 are resisted by a spiral spring 84 attached to the upper end of the shaft 38. The other end of this spiral spring is attached to a metal plate 88 clamped between the nut 84 and the adjacent surface of the block 48. The

plate 88 has anvopening 98 for receiving the cuplike upward central projection of the block 48, and the plate 9S can be pivoted about this projection for purposes of adjustment. To permit such pivotal-adjustment, the plate 98 has an arcuate slot |88 for receiving the bolt 88, and by loosening the nut 84 the plate 98 may be pivoted about the axis of the shaft 38 to adjust the tension of the spiral spring 84, and thereafter the nut 84 is tightened to clamp the plate 88 in adjusted position.

l have provided means to limit the movement of the shaft 38 under the influence of the spiral spring 84, and such means determines the stationary position of the shaft 38 and associated contact finger 84. This means comprises a stop member |82 of insulating material and rigid with the hub 18. This stop member |82 has a projection for engaging the depending finger |84 of a metal annulus |88 supported on a shoulder A pin ||8 preis also grounded to the frame of the automobile. The other end of the resistance wire 18 of this resistance is connected by a short lead ||8 to a plate ||8 adjustably located in a recess provided in the insulating block 48. The plate ||8 has an arcuate slot |28 receiving the upper end of a stud |22, the plate being held in place by a nut |24 threadedly engaging the upper end of the stud |22. The lower end of the stud |22 passes through and is in electrical engagement with the annulus |88 whereby an electrical communication is established between the lead ||8 and the casting |8. The casting I8 is directly or indirectly attached to and therefore grounded to the frame of the automobile or other vehicle and forms a ground for the resistance 12.

The foregoing arrangement permits ready adjustment of the position of the resistance 12 relative to the stop finger |84. The resistance 12 may be angularly shifted in the annular groove formed by the blocks 48 and 18, and this movement of the resistance 12 can be accommodated by pivoting 'the tongue of the terminal ||4 about the terminal 82 and by shifting the relation of the arcuate slot |28 of the terminal ||8 and by shifting the relation of the arcuate slot |28 of the terminal ||8 relative to the stud |22.

The block 48 and attached parts are held against rotation and longitudinal displacement by a set screw |28. These parts are also held against longitudinal displacement by a metal ring |28. The upper end of the sending unit is closed by a cover comprising a disk 38 of insulating material and a metal cap |32. Screws |34 attach the cap |32, plate |38 `and ring |28 to the upper end of the casting i8.

Terminals 88 and 82 project through suitable openings provided in the disk I 38 and cap |32. Each terminal is surrounded by a stepped sleeve |38 of insulating material above which is a metal washer 38 and nut |48 for attaching an end of a wire to each terminal. It is to be noted that each terminal and its associated wire is separated from the metal cap |32 to prevent grounding of either connection therethrough.

I preferably provide the casting |8 with an opening which is shown as being closed by a plug |4|. This opening is for permitting the insertion during the assembly operation of a clearance gauge between the collar 33 and the end of the bushing |8, while the lip 35 at the opposite end of shaft 28 is peened over the collar 31.

The magnet shaft 28 comprises a worm |42 for driving a cross shaft |44 mounted in bushings |48 and |48 carried in the lower part of the casting |8. This cross shaft has a worm |58 for driving a stub shaft |52 rotatable in bushings |54 and 58 also mounted in the lower portion of the casting I8. The chain of connections thus far described comprises a speed-reducing drive for a cam |58 formed on the end of the stub shaft |52.

This cam |58 constitutes a means for closing a switch |88 having a stationary contact |82 carried on an arm |84 attached to the head of a terminal |88 carried by an insulating cover 88 suitably attached to the casting I8 to close a pocket formed therein. The movable contact |18 is mounted on a resilient arm |12 attached to the casting |8 by a screw |14.

The tension of the resilient arm |12 is such that it tends to open the switch |88 and holds the tail |18 in contact with the cam |88. This cam is formed by simply cutting off the end of the shaft |82 at an angle, as clearly shown in Figure 3 of the drawings. As this cam |88 rotates, the switch |80 opens and closes at periodic intervals, bearing a definite relation to the rotation of the driving shaft 24 and therefore bearing a definite relation to the distance traveled by the vehicle. It is to be understood that the switch-carrying arm |84 is made sufficiently resilient to yield slightly when the switch contacts |82 and |10 are engaged.

From the foregoing description of my improved sending unit for electric speedometers, it

will be appreciated that I have invented a sending unit which is simple to manufacture, easy to assemble, and which may be adjusted conveniently for proper calibration. Particular attention is called to the fact that the main casting I0 provides the field plate for the magnet 28 and that the annular plate |08 is also made of iron or other magnetic material and constitutes a continuation of this field plate whereby maximum eillciency is achieved.

In order to facilitate assembly, I have so designed my improved sending unit that the insulating blocks 48 and 18, and all of the parts attached to or carried by these blocks, may be readily formed as a sub-assembly before insertion in the upper end of the casting I0. Furthermore, most of the relationships of this subassembly are independent of the rest of the mechanism, and those that are related to the rest of the mechanism, such as the relationship between the stop |04 and the spring 94 and resistance 12 can be readily adjusted after the sub-assembly has been placed in the casting I0.

Another feature of my invention lies in those design characteristics which prevent the operation of the sending unit from being affected by vehicle vibration.' In this connection, I wish tc call particular attention to the short lengthv of the resilient part of the contact finger 84 and the rigid support for this resilient part, and also the firm and protective support provided for the resistance 12.

The short leads for the resistance 12 materially improve the sensitiveness and accuracy of the sending unit by reducing the amount of the nonvariable resistance in the circuit of which this resistance 12-forms a part. The provision for accurate adjustment of the resistance relative to the contact finger 84 and its stop |04 also contribute to the accuracy of the instrument. The simplicity and ruggednessof the design of my sending unit materially contribute to the long life of the unit and the maintenance of accurate calibration throughout this long life.

In Figure 1 of the drawings I have diagrammatically illustrated the electrical circuit in which my sending unit is used and the indicating means connected with this circuit.` In this Figure 1 I have shown a conventional automobile battery |80 which is grounded to the automobile frame at |82. The other side of the battery |80 is connected to the usual ignition switch |84 which controls the usual engine ignition system, not shown. In addition to controlling the engine ignition, this switch |84 also controls three balanced circuits A, B and C, which form part of the electric speedometer. The circuit A includes motor coils |88 and |88 and is grounded to the automobile framev at |90. The coils |88 and |88 act in opposite directions on a pivoted armature |8| which controls a pointer |82 moving over a scale for indicating the vehicle speed.

The second circuit B includes the resistance 12,

one end of which is connected to the ignition switch |84 by way of terminal 82 and wire |94, and the other end of which is grounded through the casing of the sending unit, as best shown in .Figure 4. The circuits A and B are in parallel,

and the relative strengths of coils |88 and |88 in circuit A are controlled by movement of the contact finger 84 over the resistance 12 of circuit B. This contact'nger 84 is connected through its supporting shaft 38, plate 88, termineral 80 and wire |98 with a point |98` of circuit A which is located intermediate the coils |88 and |88. Since lthe position of the contact finger 84 with respect to the resistance 12 is accurately determined at all times by the speed of the vehicle, the pointer |92 of the indicating means accurately indicates vehicle speed.

The -third circuit C includes an electromagnet |99 and switch |80 and is likewise grounded to the vehicle frame through the casting I0. The electromagnet |99 periodically attr-acts an armature 200 and thereby actuates a pawl 202 which engages a ratchet wheel 204 attached to the drum of a mileage indicator.

It will be understood that the speed and mileage indicators are preferably located on'the instrument ooard of a vehicle in such position that they may be readily seen by the driver. Because of the balanced relationship between the circuits A, B and C and the design of these circuits and cooperating instrumentalities the speed and mileage indicating means may be mounted in the same casing, if so desired.

In Figures 5 to 10 of the drawings, I have illustrated another form of my invention which is essentially the same as that shown in Figures 1 to 4,

but which represents several improvements thereover. Referring to Figure 5, I have shown the preferred form` of my invention as having a combined field plate and housing 2 I0 comprising a steel sleeve, to one end of which is diecast a base 2|2 which carries the magnet shaft 2|4 for rotating the magnet 2|8. 'I'he diecast base 2|2 has a threaded end 2|8 whereby the entire unit may be attached to a transmission part like the part 4 shown in Figure 1 of the-drawings. It is to be understood that the magnet shaft 2 |4 is connected in driving relationship with a driving shaft like the shaft 24 of Figure 1 of the drawings, the magnet shaft2l4 being provided with a rectangular opening 2|5 for this purpose.

As shown most clearly in Figures 6 and 7, the diecast base 2|2 is provided with a pair of laterally extending lugs 220 having openings 222 for receiving bolts or other attaching means whereby the entire unit may be secured to the frame or other part of an automobile. The lugs 220 may be used either separately or in combination with the-threaded portion 2|8 to provide a more rigid support for the sending unit. In instances where the magnet shaft 2|4 is connected to a rotating part of an automobile by means of' a flexible driving connection, the lugs 220 will form the sole support for the sending unit.

'I'he substitution of the steel -sleeve 2|0 and diecast base 2|2 for the unitary iron casting |0 of the embodiment of Figures 1 to 4 reduces the weight of the sending unit, and in this respect the form shown in Figure 5 is an improvement over that shown in Figure 1. Both the iron casting I0 of Figure 1 and the steel sleeve 2|0 and die casting 2i2 of Figure 5 are entirely satisfactory from an operating standpoint.

In the embodiment of Figure 5, the combined bearing support and oil shield 224 is attached to the die casting 2 I2 by studs 226 which receive nuts 223 and metal washers 236. Resilient washers 232 of rubber or other suitable material are interposed between the metal washers 236 and the adjacent shoulder of the die casting 2l2. These resilient washers 232 form a seal which prevents leakage of water or foreign matter into the chamber containing the magnet 2I6, and these washers 232 have the further function of forming a cushion which prevents injury to the parts when the nuts 223 are tightened.

'Ihe form of my invention shown in Figure 5 also includes improved bearing means for the shaft 234 which carries the speed cup 236 and the pointer 233. The lower end of the shaft 234 is held against lateral displacement by a jewel 246 confined between plate 242 and flange 244 of the support 224. The lower end of the shaft 234 rests upon a jewel 246 carried in a movable holder 243 urged upwardly by a spring 256 resting upon the bottom of a cup 252 attached to the under side of the bearing support 224.

The spring 256 normally holds the holder 243 so that its upper end rests against the flange f 244. Whenever the sending unit is suibjected to a shock or jar which urges the shaft 234 downwardly against the bearing 246, the spring 256 yields slightly and absorbs the shock whereby damage to the parts is prevented and the life of the sending unit is materially prolonged. The amount of movement permitted the bearing 243 is so slight that the corresponding movement of the shaft 2'34 with its speed cup 236 and pointer 236 does not `interfere with the operation of the instrument.

The upper end of the shaft 234 is held against lateral displacement by a jewel 254 located in a recess formed in the central portion of the insulator block 256 and held in place by a metal plate 253. A screw plug 236, adjustably mounted in finger 262, constitutes an adjustable end thrust bearing for the shaft 234.

The insulator block 256 is secured to the upper end of the steel sleeve 2I6 by screws 264 which pass through the upper end of the sleeve 216 and engage in an annular recess 266 formed in the lower end of the block 256. The insulator blocks 253 and 263 cooperate to provide a recess for receiving the resistance 216, as in the previous embodiment. It will be understood that these blocks 256 and 266 are preferably'formed of a phenol condensation product or other suitable material.

Another feature of the embodiment shown in Figure 5 is the improved means for securing the cover to the sending unit. This cover 212 is attached to the unit by means of bolts 214 and 21,6, whose heads are molded into the :block 263. The cover 212 has eyes 21-3 and 286 which surround bolts 214 and 216, respectively. The eye 213 is confined between nuts 282 and 234, and the eye 236 is confined between nuts 236 and 233. The open end of the cover simply slides over the adjacent end of the sleeve 2I6, and the arrangement is such that tightening of the nuts 264 and 233 to secure the cover firmly in place does not tend to pull the bolts 214 and 216 out of the insulator blocks 256 and 233.

The spring 266 for resisting rotation of the shaft 234 has one end attached at 262 to an adjustable plate 264, as in the previous embodiment. The spring 236 with its supporting Piate 264 and the finger 262, both .serve to tablish an electrical connection between the pointer 233 and the bolt 214 which forms one terminal of the sending unit. The end 293 of the resistance 216 is connected to a metal strip 264 carried on the bolt 216 which forms another electrical terminal of the sending unit. The other end of the resistance 216 is grounded through plate 233, as in the previous embodiment. This plate 266. like the corresponding plate of the previous embodiment, is made of magnetic material and constitutes a continuation of the field plate, and this plate 266 also forms a stop for the shaft 234.

The embodiment of Figures 5 to 10 also includes an improved 'form of switch mechanism for controlling the odometer. As best shown 'in Figures 5, 9 and 10, the magnet shaft 2|4 drives a cross shaft 366 .which in turn drives a stub shaft 362 carrying aswitch operating oam 364. This cam contacts and moves the resilient switch arm 366 carrying movable contact 363 which is adapted to cooperate with a stationary contact 3i6 mounted on a second switch arm 3I2 which may be slightly resilient, if desired.

The cam 364 is of the single lobe type and is designed to open and close a switch formed by the contacts 366 and 3|6 once for each revolution of the shaft 362, the cam being especially designed to give a substantially uniform movement to the finger 366 and to prevent sudden engagement or disengagement of the contacts 363 and 3I6.

The resilient finger 366 is grounded to the automobile frame by being directly attached to the die casting 2|2, as by means of screw 3|4. The switch arm 3|! is connected to bolt 3I6 which is insulated from its supporting plate 3I3 by insulating disks 326, 622 and 324.

It is to be understood that the preferred form of my sending unit shown in Figures 5 to 10, inclus-ive, is intended to be connected into an electrical circuit in the manner indicated in Fig- T ure 1 in connection with the earlier form of my invention. It will further'be understood that the mode of operation of the sending unit shown in Figures 5 to 10, inclusive, is the same as that of the sending unit shown in Figures 1 to 4..

While I have illustrated and described only two forms of my invention, it is to be understood that -my invention may assume numerous forms and that the scope of my invention is therefore limited solely by the following claims.

I claim:

1. In a sending unit for electric speedometers, the combination of a magnet shaft, a magnet driven thereby, a speed cup associated with said magnet, a variable rheostat controlled by said speed cup, and a single casting enclosing said shaft, magnet, speed cu-p and rheostat, and forming a eld plate for said magnet.

2. In a sending unit for electric speedom'eters of the class described, the combination of a casting, a shaft rotatably mounted therein, a magnet driven by said shaft, a speed cup rotatably supported in spaced relation to said magnet, said casting having a portion enclosing said magnet and speed cup and forming a field plate for said magnet, and means controlled by said speed cup.

3. In a sending unit of the class described, the combination of a casting having a base and cylindrical portions of two internal diameters, a shaft mounted in said base,Y a magnet driven by said shaft, a speed cup associated with said magsaid magnet, a variable resistance controlled by I said speed cup, and a second member forming a continuation of said field plate and a grounding connection for said resistance.

5. In a sending unit for electric speedometers, the combination of a shaft, a contaict finger mounted thereon, a spring for moving said contact finger in one direction, means for moving said contact finger in the other direction, and

a sub-assembly comprising a resistance for cooperation with said finger, means adjustably supporting said resistance, an adjustable terminal for each end of said resistance, an adjustable support for said spring, and a stop for said contact finger.

6. In a sending unit for electric speedometers, the combination of a magnet shaft, a magnet driven thereby, a speed cup associated with said magnet, a. variable rheostat controlled by said speed cup, and a unitary structure enclosing said shaft, magnet, speed cup and rheostat and forming a field plate for said magnet.

7. In a sending unit for electric speedometers, the combination of a magnet shaft, al magnet driven thereby, a speed cup associated with said magnet, a variable rheostat controlled by said speed cup, and a unitary structure enclosing said shaft, magnet, speed cup and rheostat, said structure comprising a sleeve forming a field plate for said magnet and a basedie cast to one end of said sleeve.

8. In a'sending unit for electric speedometers, the combination of a magnet shaft, a magnet driven thereby, a speed cup associated with said magnet, a variable rheostat controlled by said speed cup, a steel sleeve forming a eld plate for said magnet, and a base4 die cast to said, sleeve, said base providing lugs for attaching said unit to a support.

9. In a device of the class described, the combination of a shaft, electromagneticl means for rotating said shaft, a thrust bearing for said shaft, and a resilient support for said bearing.

10. In an instrument of the class described, the combination of a shaft, electromagnetic means for rotating said shaft, a thrust bearing for one end of said shaft, a resilient support for said bearing, and an adjustable thrust bearingl for the, other end of said shaft.

11. In a sending unit for electric speedometers of the class described, the combination of a magnet, means for rotating said magnet, a speed cup associated with said magnet, a shaft supporting said speed cup, a jewel thrust bearing for one end of said shaft, a slidable metallic support for said bearing, a spring urging said support in one direction, means limiting movement of said bearing in the opposite direction, and bearing means for the other end of said shaft.

12. In a sending unit for electric speedometers, the combination of a magnet shaft, a magnetdriven thereby, a speed cup associated with said magnet, a variable rheostat controlled by Said speed cup, an enclosing structure, an insulator block carried by said structure, a bolt provided 0n,said block, a cover slidably related to said structure, and a pair of nuts on said bolt engaging opposite sides of said cover and securing said cover to said structure.

' 13. In a sending unit for electric speedometers, the combination of a magnet shaft, a magnet driven thereby, a speed cup associated with said magnet, a second shaft supporting said cup, a bearing support for said second shaft, a base having an opening therethrough, a stud attached to said bearing support and passing through said opening, a nut secured to the end of said stud, and a resilient washer interposed between said nut and said base and forming a., seal and cushion therebetween. f'

-defining an inwardly facing annular channel, re-

Isistance means held in place between said blocks, an annular field plate for completing the field, and a terminal for said resistance means for securing the blocks and plate together.

ARDEN W. LE FEVRE. 

